1. Field of the Invention
The present invention relates generally to the fields of dermatology and cosmetology, and particularly relates to the application of chromophore compositions to the skin so as to target hair follicles prior to the application of electromagnetic irradiation.
2. Information Disclosure Statement
A main function of mammalian hair is to provide environmental protection. However, that function has largely been lost in humans, on whom hair is usually kept or removed from various parts of the body for cosmetic reasons.
Various procedures have been employed to remove unwanted hair, including shaving, electrolysis, the use of depilatory creams or lotions, waxing, plucking, therapeutic anti-androgens, lasers and lamps. These conventional procedures each have significant drawbacks, and most often only result in temporary hair removal. Although electrolysis or electrothermolysis can provide permanent hair removal, these painful and tedious techniques rely on operator skill and require multiple treatments. Therefore, the permanent removal of unwanted hair without the risk of the occurrence of folliculitis, scarring or infections (which often occurs after electrolysis) is difficult to achieve.
It has been disclosed that selective photothermolysis (through the use of Ruby lasers, Alexandrite lasers, Nd:YAG lasers, pulsed diode lasers, or pulsed light) is an effective method for destroying pigmented hair follicles. The thermal effects generated during laser irradiation are principally responsible for hair follicle alteration and destruction. In these procedures, thermal damage to the hair follicle is the consequence of laser light absorption by endogenous melanin. However, results are essentially dependent on hair pigmentation, quantity of melanin present in hair (depending on color, hair diameter, hair cycle, position on the body . . . etc) and the ratio between melanin concentration in the hair bulb and in the epidermis. For these reasons, hair removal methods using lasers or light alone give poor results for light-colored hairs (blond, auburn and white) and can burn and/or produce discoloration of darker skin.
Many systems have been developed to counteract these negative effects, such as cooling apparatuses, or the use of pulsed, sequenced or alternating laser pulses. In addition to pure laser applications, other methods have been disclosed, including the use of exogenous chromophore to increase the light absorption efficiency of the hair follicle in comparison with endogenous melanin absorption, and thus increase the safety of the procedure by reducing the laser power needed.
Tankovich, in U.S. Pat. No. 5,425,728, suggested that the photothermolitic effects of the lasers could be enhanced by utilizing contaminants with a high absorption of certain laser wavelength. The contaminants suggested included carbon in peach oil that, with massage or ultrasound, could be used to force the carbon into the hair ducts. For this contaminant, a CO2 laser was recommended with pulses between 200 and 275 nanoseconds. An alternative method uses a near infrared laser at about 1,060 nm but with pulses in the range of 25-30 picoseconds. Another alternative utilizes a staining technique and matched the laser to the stain selected. Yet another method used a photosensitizer which made the entire hair shaft susceptible to the applied laser. These most recent laser methods using red and infrared wavelength are much quicker than the earlier treatments in that the laser can act upon a group of hairs in a fraction of a second. Also, the use of the laser is somewhat less painful and has a much lower risk of infection and scarring than any of the non-laser methods mentioned above. However, these previous carbon-based formulations are not able to specifically target hair follicles. (for example, carbon particles are found within stratum corneum).
In the patent to Schaefer, U.S. Pat. No. 5,292,512, it was suggested that only a particular diameter of microspheres could be used to specifically target hair follicles. In the case of human skin, Schaefer claims that microspheres with a diameter greater than 10 xcexcm do not settle into the follicular duct, whereas microspheres with a size smaller than 3 xcexcm penetrate both the stratum corneum and the follicular duct. As a result, Schaefer claims that active substances encapsulated in microspheres within this size range can be specifically targeted to the hair follicle. Rolland A et al., xe2x80x9cSite-specific drug delivery to pilosebaceous structures using polymeric microspheresxe2x80x9d, Pharmaceutical Research 10: 1738-44 (1993) clearly demonstrated this by following the localization process of fluorescent microspheres to hair follicles. Small microspheres ( less than 1 xcexcm in diameter) entered into follicles as well as the upper 2-3 cellular layers of the stratum corneum and thus appeared to be spread over the skin. In contrast, medium size microspheres (around 5 xcexcm) entered in the follicles but did not penetrate the upper layers of the stratum corneum. This results in an apparent targeting of these microspheres to hair follicles. Large microspheres ( greater than 10 xcexcm) were excluded from penetrating into either of these sites. Consequently, appropriate choice of particle size facilitates specific follicular targeting. However, these particles can only penetrate the follicle to depths corresponding to 200-300 xcexcm below the skin surface, which is not sufficient to destroy cells in the root of the follicle. Also, these particles still can still enter and cause damage to other areas of the skin, such as the channels of sweat glands.
Photosensitizers and, in general, exogenous compounds used in conjunction with light (exogenous chromophores) are not considered an xe2x80x9cactive substancexe2x80x9d (these compounds are only xe2x80x9cactivexe2x80x9d under light) and one other approach was described to encapsulate at least one exogenous chromophore in this microsphere size range (3-10 microns in diameter) to obtain specific follicular targeting before laser irradiation. This approach is described in U.S. Pat. No. 6,287,549 by Sumian et al. However, Sumian C et al. reports in xe2x80x9cA new method to improve penetration depth of dyes into the follicular duct: Potential application for laser hair removalxe2x80x9d, J. Am. Acac. Dermatol., 41:172-5 (1999), that dyes (e.g. Rhodamine 6G) can be specifically positioned in the follicle if the dye is encapsulated in size-defined microspheres (around 5 xcexcm in diameter) and diffusion outside the microspheres is induced. This diffusion can reach 500 xcexcm below the skin surface (with the appropriate vehicle). After diffusion, compounds may stay in hair follicles to induce a specific action and/or diffuse into the dermal tissue. Penetration and diffusion of compounds/drugs inside hair follicles depends on the formulation vehicle and the molecule""s ability to pass through a collapsed follicle, particularly its size, molecular weight and solubility. Even if diffusion occurs, the compound/drug flux is limited by those follicles that have collapsed after the initial hair removal. In addition, these microparticles do not only target the hair follicle; some microparticles can be found in the channels of sweat glands. Because sweat glands help to regulate body temperature by manufacturing and excreting sweat onto the skin surface, alteration of their excretory channels after laser irradiation can produce a xe2x80x9cdangerousxe2x80x9d temperature deregulation of the body, and is thus an occurrence that should be avoided.
Klopotek, U.S. Pat. No. 6,074,385, discloses a method in which magnetic particles are utilized to remove hair. Hair is first manually removed from the follicles, then particles are applied to the skin by a method that will force the particles into the follicle, such as including them in a dry slurry or a lotion. Another method would be to force them into the skin using a magnetic field. A composition consisting of magnetic particles of a size small enough (5 Angstroms-100 microns, preferably 50 Angstroms-10 microns) so that at least some of them will fit in the follicle. A magnetic field is then applied to the treatment area, which causes the particles to heat up and destroy the papilla or other vital structure in the hair follicle.
The prior art teaches the use of microparticles in hair removal, but does not disclose an effective method for preventing absorption of microparticles in other areas of the skin, such as sweat gland channels. The act of rubbing the particles, whether in a dry or other type of composition, may cause some particles to be imbedded in the skin in areas other than the follicle. This could result in damage to or discoloration of the skin. Because chromophores are not efficiently targeted to the hair follicle, only a small portion of the applied energy is actually absorbed by the follicle, and the rest is absorbed by the skin. Thus, unless the energy applied is localized to an individual hair follicle (which is very time-consuming), present applications allow absorbing particles to enter other parts of the skin and cause damage. In order to induce only hair follicle injury without damaging surrounding tissues, greater hair follicle specificity is needed. By increasing both the quantity of chromophore delivered into the follicle and the penetration depth of the chromophore into the follicular duct, the efficacy of hair removal could be improved independent of hair color.
For the foregoing reasons, there is a need to develop new methods that are efficiently and easily administered, non-irritating, able to primarily target hair follicles, and capable of depositing chromophore deeply along the hair follicles to reduce or prevent hair regrowth.
It is an object of the present invention to provide a method for microparticle follicle targeting that addresses the deficiencies in the prior art.
It is another object of the present invention to provide topical compositions able to primarily target hair follicles after the removal of hair from the follicles, and thus provide compositions able to selectively introduce compounds or drugs into hair follicles.
It is a further object of this invention to provide a method where microparticles can be introduced into hair follicles without being absorbed by other appendages of the skin.
It is yet another object of this invention to provide a method where particles can be introduced that solely target the hair follicle, while leaving the sebaceous gland unaffected.
It is another object of the present invention to provide topical compositions able to selectively introduce photosensitizers and/or sonosensitizers into hair follicles prior to the application of electromagnetic irradiation on the area to be treated, and thus reduce or prevent the regrowth of hair.
It is still another object of the present invention to provide topical compositions containing different size and/or shape of microparticles to target all diameters and shapes of hair follicles.
Briefly stated, the present invention provides a device and method for permanent or semi-permanent removal of hair through the activation of microparticles introduced into hair follicles. Microparticles are incorporated into a composition that is topically applied to the skin. These microparticles containing or consisting of chromophores or chemically activated molecules are of a variety of shapes and sizes. Microparticles are within a size range of 1 micron to 70 microns, and preferably between 10 and 50 microns. Microparticles of this size and variety of shapes enter hair follicles on all areas of the skin without entering other areas of the skin, such as the stratum corneum or sweat gland channels. Treatment of the skin with electromagnetic radiation delivered by a laser or a non-coherent radiation-emitting lamp, ultrasonic radiation or chemical means activates the chromophores or chemically activated molecules, thus destroying the hair follicle without damaging other areas of the skin. In another embodiment, microparticles further contain nanoparticles released further into the hair follicle by use of a solvent or other method, allowing chromophores or chemically activated molecules to penetrate deeper into the follicle and avoid structures such as the sebaceous gland.
The above, and other objects, features and advantages of the present invention will become apparent from the following description read in conjunction with the accompanying drawings.